Note: This bottom line does not include marjoram (Origanum majorana). This is discussed in the marjoram bottom line. The main species of interest in this bottom line is Origanum vulgare. However, due to the nature of oregano and the use of more than one species in the commercial spice, other species are discussed.

Oregano is an herb that has been used to preserve and add flavor to food. The leaves, stems, and flowers have been used as medicine for menstrual, lung, and stomach or intestinal disorders.

Modern herbalists recommend taking oregano oil by mouth or applying it to the skin to treat infection. Strong human evidence for any clinical use of oregano is lacking.

Oregano is thought to have antifungal, antioxidant, antibacterial, and insect-repelling effects, although evidence is mixed. The antibacterial and antioxidant effects of oregano are of interest to the food industry as oregano may hold promise as a natural preservative.

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

GRADE *

The use of an herbal infusion containing oregano has been studied for use after tooth removal in people with hemophilia, a bleeding disorder. More research is needed in this area.

C

Early research suggests that oregano may improve cholesterol levels and heart disease risk. However, further study is needed before conclusions can be made.

C

Early study shows that taking oregano oil by mouth for six weeks may help treat some parasite infections. While promising, further research is needed to confirm these results.

C

Early study suggests that an ointment containing oregano may improve color and scar softness as well as reduce bacteria. However, more research is needed in this field.

C

* Key to grades

A: Strong scientific evidence for this useB: Good scientific evidence for this useC: Unclear scientific evidence for this useD: Fair scientific evidence for this use (it may not work)F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory
The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

Oregano has been taken by mouth in the following forms: capsules (containing 45 milligrams of pure oregano oil), 1-3 times daily with meals; 250-500 milligrams of leaf extract three times daily; 3-6 drops of oil, pure or diluted with olive oil, added to milk or juice 1-2 times daily; and a tea made from hot water and finely ground herb. Traditionally, 5-6 drops of oregano oil have been taken by mouth 2-3 times daily with sugar, and 1-4 drops of oregano tincture have been diluted in water and taken by mouth 2-3 times daily.

For heart disease prevention, 25 milliliters of oregano distillate have been taken by mouth after each meal for three months.

For the prevention of bleeding after tooth removal, 30 milliliters of an oregano infusion have been taken by mouth six times daily for 10 days.

For parasites, 200 milligrams of oregano oil have been taken by mouth three times daily with meals for six weeks.

For the common cold, 1-3 drops of oregano oil have been taken by mouth in a teaspoon of olive oil.

For cosmetic uses, oregano oil has been added to commercial shampoo and applied to the hair for a few minutes before rinsing.

For wound healing, a 3 percent oregano extract ointment has been applied to the skin twice daily for 10-14 days.

Children (under 18 years old)

There is no proven safe or effective dose for oregano in children.

Safety
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Avoid in people with known allergy or sensitivity to oregano, its parts, and other members of the Lamiaceae family.

Oregano is likely safe when taken by mouth in amounts commonly found in foods by non-allergic individuals. Oregano leaf and oil have been given GRAS (Generally Recognized As Safe) status by the U.S. Food and Drug Administration (FDA).

Oregano may increase the risk of bleeding. Caution is advised in people with bleeding disorders or taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary.

Oregano may lower blood sugar levels. Caution is advised in people with diabetes or low blood sugar, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood sugar levels may need to be monitored by a qualified healthcare professional, including a pharmacist, and medication adjustments may be necessary.

Oregano may cause low blood pressure. Caution is advised in people taking drugs or herbs and supplements that lower blood pressure.

Use cautiously in people who have autoimmune disorders.

Use cautiously in people who take agents that affect the immune system, CNS depressants, and mineral supplements.

Use cautiously in children, due to a lack of safety information.

Avoid in pregnant women when using at levels greater than those found in the diet, or when using the herbal combination product Carachipita®.

Avoid in people with known allergy or sensitivity to oregano, its parts, and other members of the Lamiaceae family.

Pregnancy and Breastfeeding

There is a lack of scientific evidence on the use of oregano during pregnancy or breastfeeding. Avoid in pregnant women when using at levels greater than those found in the diet, or when using the herbal combination product Carachipita®. Oregano in medicinal amounts may cause abortion.

Oregano may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

Oregano may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

Oregano may interfere with the way the body processes certain drugs using the liver's "cytochrome P450" enzyme system. As a result, the levels of these drugs may be altered in the blood, and may cause altered effects or potentially serious adverse reactions. People using any medications should check the package insert, and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.

Oregano may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.

Oregano may interfere with the way the body processes certain herbs or supplements using the liver's "cytochrome P450" enzyme system. As a result, the levels of other herbs or supplements may be altered in the blood. It may also alter the effects that other herbs or supplements possibly have on the P450 system.

Oregano may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.

Oregano may cause low blood pressure. Caution is advised in people taking herbs or supplements that lower blood pressure.

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.